Trouble Shooting Guide

AnomalyPossible CauseRemedy
Cryostat body wet after liquid nitrogen filling.

Poor vacuum.

Vacuum valve not fully closed.

Vacuum leak.

Pump the vacuum.

Close the vacuum valve.

Pump continuously and inform us.

Cryostat will not receive liquid helium.

No liquid nitrogen.

Helium leak.

Contact between shields.

Fill liquid nitrogen bath.

Pump continuously and inform us.

Return the cryostat to our lab.

Sample cools badly and high flow necessary to stabilise T < 50K.Contact between shields.Return the cryostat to our lab.
Cold valve blocked.Cryostat badly flushed.Reheat to 300K and inform us.
Temperature rises rapidly after closing cold valve.Sample still warm.Wait for thermal equilibrium of sample and exchanger.
Cooling difficult with temperature oscillations.Wrong PID settings and/or too much exchange gas.Check the PID settings, set T=10K and pump via exchange gas valve to <1mbar.

Fluctuations at low temperature (T<4.2 K), unstable cold valve pressure, cold valve pressure rise when heating

Liquid helium in the annular enclosure (tail).Close cold valve, set T=10K and wait until the pressure drops to < 2mbar.
Temperature rises for no apparent reason.Lack of liquid nitrogen and/or liquid helium.Verify the liquid helium and liquid nitrogen levels, refill.
Sample stick stuck in cryostat.Air leak into sample well.Go to 150K by step of 20K with the clamp slightly unscrewed. DO NOT FORCE AND DO NOT STAY ABOVE THE STICK.